I am retrieving an old tube radio. How can I tell when a tube is weak or in trouble?
A burnt tube, that is, with a broken filament, can be easily tested with the multimeter or even with a visual inspection of the connected circuit. The burnt tube does not light. However, there are other problems that can occur and that we can detect without the need for a tester. For example, if the side or top where the getter is white is a sign that air has entered and the tube is unusable.
